Washing platelets with new additive solutions: aspects on the in vitro quality after 48 hours of storage

Rare clinical conditions cause the need for washed platelet (PLT) concentrates (PCs). Saline-washed PCs can only be stored shortly, however, owing to lack of substrates for PLT metabolism. New PLT additive solutions (PASs) contain such substrates and might be used alternatively. The in vitro quality of apheresis PCs washed with Composol-PS or modified PAS-III (PAS-IIIM) stored up to 48 hours after wash was compared.

Twelve blood donors underwent two apheresis procedures (A and B) collecting 6.0 x 10(11) PLTs in 500 mL of plasma with a least 2 weeks in between. The PCs collected by Apheresis A were stored for 3 days and then split in two equal units before washing with Composol-PS or PAS-IIIM. The PCs collected by Apheresis B were split after collection. One unit was released for transfusion and 1 unit was stored unwashed up to Day 6 and used as reference unit. In vitro testing was performed before and after washing as well as 24 and 48 hours after wash.

After 48 hours of postwash storage, the units washed with either PAS showed acceptable results for hypotonic shock response (HSR), P-selectin expression, and pH, whereas PLT aggregability was significantly impaired. Throughout the storage, unwashed units showed better in vitro quality. HSR and P-selectin expression were similar before and immediately after the washing procedure.

Based on these in vitro results, 48-hour postwash storage of washed PCs with the two PASs seems to be feasible. In vivo recovery studies, however, must confirm this finding in the future.